A Congolese health worker administers Ebola vaccine to a woman in North Kivu.
Photograph: Olivia Acland/Reuters

An outbreak of Ebola in the Democratic Republic of the Congo (DRC) has reached a pivotal moment and now endangers medical teams fighting to stop the spread of the disease, health workers have said.

Dr Peter Salama, the World Health Organisation’s emergencies chief, said there were 103 confirmed and probable cases in the outbreak, which is centred in the eastern province of North Kivu, and that another wave of cases was expected.

The DRC’s Health Ministry has confirmed 36 deaths. Another 27 deaths were suspected to be from Ebola, it said. Salama said 14 healthcare workers had been infected so far, one of whom had died.

Several cases of Ebola have already been identified in the city of Beni, raising fears of further infection in a crowded urban centre.

Just as worrying, health workers said, was a new case in the town of Oicha, which is almost entirely surrounded by an Islamist militia based in Uganda that has been responsible for a series of bloody raids across the region.

North Kivu is one of the most violent parts of Congo, and is a base for dozens of armed groups that contest government authority and exploit mineral resources in the region.

The WHO said a doctor in Oicha had been hospitalised with Ebola, and 97 of his contacts had been identified. “It is the first time we have a confirmed case and contacts in an area of high insecurity. It is really the problem we were anticipating and at the same time dreading,” Salama said.

Karin Huster, coordinator for Médecins Sans Frontières in Mangina, the epicentre of the outbreak, said new patients were arriving at the emergency treatment units every day.

“Obviously we are concerned. We are worried that we are not seeing the suspect cases coming into our centres that we should be seeing. It is not a situation where we are confident that the outbreak is under control,” Huster said. “It is all about winning the trust of the community. It’s super important to come early when they are sick and people often come too late.”

The insecurity in the region and a mobile population has made vaccination campaigns like the one that helped overcome an Ebola outbreak that killed 33 in the north-west of the DRC earlier this year less effective.

Oly Ilunga, the minister of health, was more optimistic. “The situation seems to be stabilising following the different measures we have taken. But we must be prudent and remain prudent over coming weeks,” Ilunga said.

Authorities have now approved a total of five experimental treatments against the virus in the hope they will help stop its spread.

Prof Steve Ahuka, a virologist at the DRC’s national institute of biomedical research, said two brand new treatments were already being used on 10 patients, of whom two had been discharged after doctors decided they were out of danger. “We always ask for the consent of the patients. So far no patient has ever opposed being treated with these medicines,” Ahuka, who is in Beni, said.

A significant problem is the belief among many local communities in and around Beni that the outbreak has been caused by sorcery, local civil society activists said.

“We’ve been trying to show people that Ebola is a disease that we’ve seen 10 times now in the DRC … When there is a case in a red zone [where security is poor] we call on Congolese army soldiers and the United Nations for help,” said Kizito Bin Hangi, who heads a coalition of civil society groups in Beni.

The DRC, whose heavily forested interior makes it a natural home for Ebola, is at the forefront of a global campaign to combat the virus. The biggest recorded outbreak of Ebola killed 11,300 people in Guinea, Liberia and Sierra Leone from 2014 to 2016.

Ebola first appeared near the northern Ebola river in the DRC in the 1970s. It has twice reached Kinshasa but, on both occasions, has been contained.